Eh, i can try conditioning water for future fish.. but every betta i've had has been well with spring water.
I did try conditioning for a short period, but it seemed to make them sick. So i figured i wouldn't try to fix what was not broken..
Thanks for the brand recommendations though, those could maybe help.

According to bettatalk bottled water doesn't need to be treated with conditioner. I would use it to be on the safe side.Stresscoat helps to maintain their slime coat and when they are damaged by injury or disease.